1. Field of the Invention
The present invention relates to a flow damper.
2. Description of Related Art
A flow damper includes a valve body, a piston, a spring, and a stopper The valve body has a generally cylindrical shape, and a fuel passage is formed in the valve body. The piston slides in its axial direction along a piston sliding hole formed inside the valve body. The spring urges the piston toward an upstream side in a fuel flow direction. The stopper restricts displacement of the piston toward the upstream side (see, for example, JP2001-50141A corresponding to U.S. Pat. No. 6,357,415).
The piston has a throttle passage, which communicates between upstream and downstream sides of the fuel passage. When a fuel flow in the downstream direction in the fuel passage abnormally increases because of malfunction of an injector such as an excessive fuel outflow, the piston is moved toward the downstream side, and a valve portion of the piston engages a valve sheet of the valve body to block the fuel passage. In this manner, the flow damper stops an outflow of high-pressure fuel if some failure is caused by any possibility.
The valve body is fastened to a rail main body, which accumulates pressure of high-pressure fuel. Accordingly, a closely-attached surface between the valve body and the rail main body needs to ensure a highly oil-tight sealing surface. The valve body is fastened by strong axial force and fixed to the rail main body.
The valve body is strongly fastened to the rail main body, so that the valve body on a rail main body-side, to which strong axial force is applied, is strained.
The valve body slidably holds the piston inside the valve body. When the valve body is strained for the above reason and accordingly the piston sliding hole is deformed in a radially inward direction, a sliding clearance between the valve body and the piston is decreased, thereby deteriorating a slide of the piston.
For this reason, as shown in FIG. 6, a stopper J3 is press-fitted into the inside of a valve body J1 to which strong axial force is applied, that is, into an inner circumferential surface of an opening side of a piston sliding hole J2, in order to prevent deformation of the piston sliding hole J2.
In addition, to avoid promotion of pulsing motion generated in an injector pipe by movement of a piston J5, which is involved in a fuel flow generated when the injector (fuel injection valve) injects fuel, an orifice J4 is formed in the stopper J3.
However, since the stopper J3 is press-fitted into the valve body J3 in a production process of the flow damper, a fuel flow cannot be adjusted in the flow damper, which has been produced.
More specifically, when it is examined whether the flow damper that has been produced (in an assy state) works within an appropriate range, the stopper J3 that is press-fitted cannot be separated from the valve body J1 if the flow damper turns out to be faulty (NG). Accordingly, replacement of the stopper J3 (change of a diameter of the orifice in the stopper J3), replacement of the piston J5 (change of a diameter of a throttle passage in the piston J5), and replacement of a spring J6 (change of a set load) cannot be done.
For these reasons, in product management of the flow damper that has been produced, the flow damper itself, which has been produced, needs to be disposed of if the flow damper is outside the appropriate range.